地中壁液化防制效果之離心模型試驗

許漢維(Han-wei Shiu)

指導教授 ： 黃俊鴻 ； 李崇正

國立中央大學/工學院/土木工程學系/碩士(2014年)

摘要

本研究利用地工離心機與振動台，於50g離心重力場下進行十二組地中壁液化防制效果之離心模型試驗，並在試驗進行中擷取加速度計、孔隙水壓計、土壓計、線性差動可變變壓器(LVDT)所量測到的動態數據，藉以探討不同間距地中壁對於超額孔隙水壓激發抑制效果，並探討(1)加速度放大倍率隨深度變化；(2)不同深度超額孔隙水壓激發與消散行為；(3)地表沉陷量歷時；(4)壁體所受側向總應力歷時等課題。

研究結果顯示：(1)土壤在未達液化狀態時，振動加速度由基盤至地表逐漸放大；土壤達到液化狀態時，由於剪力波無法傳遞，所以加速度傳遞至地表面而大幅度減小；(2)地中壁的圍束作用對超額孔隙水壓激發之抑制是有效果的，且以格子間距5公尺之抑制效果最佳；(3)地中壁能有效限制地表沉陷量，以格子間距5公尺圍束區域內之地表沉陷量最小；(4)震波往上傳遞時，壁體受到側向有效土壓力與孔隙水壓往復作用，且隨深度越深壁體受力越大；(5)當超額孔隙水壓力逐漸消散時，土壤將產生沉陷並往四周壁體擠壓，所以當超額孔隙水壓消散完成時，將有殘餘應力作用於壁體上，且深度越大其值越高。

關鍵字

液化防制 ； 地中壁 ； 土壤液化 ； 地工離心機 ； 加速度放大效應 ； 沉陷量 ； 超額孔隙水壓 ； 殘餘應力

並列摘要

A series of centrifuge shaking table tests was conducted to investigate the mitigating effect on soil liquefaction by the lattice-shaped underground wall. During the test, accelerometers, pore pressure transducers, linear variable differential transformers and micro earth pressure transducers were embedded in the soil layer to monitor the seismic response of soil deposit. The mitigating effect was evaluated by the measurements, including (1) maximum peak ground acceleration along the depth; (2) excess pore pressure histories at different depths; (3) ground settlement and (4) lateral total pressure applied on the underground wall.
From the test result, it can be conclude that (1) the acceleration amplitude was amplified from the base to the surface ground before soil liquefaction. The shear wave can not propagate through the liquefied soil layer to the ground surface and leading to that the acceleration amplification was smaller than 1. (2) The lattice-shaped underground wall with 5 m-width spacing was effective to mitigate the generation of pore water pressure and to decrease the settlement of surface ground. (3)The total lateral pressure acted cyclically on the underground wall and increased with increasing depth during shaking. (4) The ground settled and the lateral earth pressure acting on the underground wall increased during the pore water pressure dissipation. Therefore, there was an additional force acted on the underground wall as compared to the initial condition.

並列關鍵字

centrifuge shaking table test ； underground wall ； soil liquefaction

參考文獻

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